Typically, emergency signalling systems include a plurality of signalling devices. For example, a system may include a siren/speaker and visual indicators such as rotating and flashing lights and auxiliary lights such as take-down lights, alley lights and headlight flashers. Different combinations of these devices are simultaneously operated in order to create signalling patterns of different types. Each type is usually designed for use in a particular category of emergency situations. For example, when a vehicle incorporating such a system is stopped on the side of the road in order to help a disabled vehicle, operation of only the flashing lights may be appropriate. When pursuing a vehicle, maximum signalling is required and the primary visual indicators (rotators) and a siren may be added to the flashing lights. A non-pursuit-type emergency may call for the primary visual indicators and the flashing lights, but no siren.
So the operator of the emergency vehicle does not have to configure his/her own emergency signalling each time the system is used, each system is typically designed to operate in one of a plurality of selectable "operating modes." Using the example of the previous paragraph, a first operating mode may operate the system with flashing lights only. A second operating mode may operate the flashing lights and the rotating lights. A third operating mode may operate all of the flashing lights, rotating lights and the siren/speaker.
Designating the functions of each operating mode, however, restricts the versatility of the system and prevents an operator from tailoring the various operating modes to the needs of his/her particular application and environment. In order to provide some versatility to the system, it is known to provide dip switches on the circuit boards of the system that allow selected signalling devices to be enabled for each operating mode. Unfortunately, the dip switches are not easily accessible and require a service technician to partially disable an installed system if the operating modes are to be changed. Moreover, they are expensive and require considerable space. In order to provide any significant amount of system versatility, a large number of the switches would be required, thereby making such a system bulky and expensive.
In addition to the selective enablement of various signalling devices for different operating modes, attempts have been made to provide the signalling devices themselves with more than one operating mode. For example, U.S. Pat. No. 4,701,743 to Pearlman et al. discloses a signalling device comprising a light source and a reflector mounted for relative rotation in two different operating modes. A first mode provides for relative rotation between two end points so that the reflector in effect oscillates through an arc. In a second mode of operation, the reflector continuously rotates the reflector in a single direction.
In order to provide for the oscillating rotation of the reflector, sensors are mounted at the end points of the oscillation so that a control circuit is informed when the reflector has completed its rotation through the arc. When the control circuit receives an indication that the reflector has reached an end point, it reverses the rotation of a motor driving the relative rotation, thereby reversing the direction of the rotation and rotating the reflector to the opposite end point where the control circuit again reverses the motor's rotation.
Although such a signalling device provides two modes of operation that can be selected by a user, the oscillatory mode is restricted by the placement of the sensors for detecting the end points of the oscillation. In order to modify the oscillatory mode, hardware modifications must be made to the signalling device. Moreover, if additional modes of operation are to be added to such a signalling device, additional expensive sensors must be provided. As additional modes of operation are added, the device very quickly becomes complex and expensive, thereby effectively making the device commercially infeasible. Furthermore, although such multi-mode signalling devices may add additional available patterns to a signalling system incorporating these devices, they provide only a small additional degree of flexibility to the system while introducing substantial complexity and expense.